you're an essayist and a critic on philosophy, mathematics and science and you have a new book called "why does the world exist: an existential detective story." >> you say that sarcastically. (laughter) >> stephen: that's as sincere as i get. (laughter) first question: why does world exist exist? (laughter) what led you to write this book? >> good question. i was raised in a very religious family. >> stephen: what kind? >> catholic. >> stephen: how religious were you? >> i said the rosary. i did--. >> stephen: basic stuff, basic stuff. >> i confessed my sins. >> stephen: are you still catholic? >> no. >> stephen: well then how religious could your family have been? evidently they failed. >> yeah, they told me this story that the world exists because god--. >> stephen: in the beginning. >> exactly. there's already a book about that, by the way. (laughter) so you listened and then at some point you said i don't buy it. >> i began to have doubts and i want to know why the universe exists. if there's a reason i want to know that and god might be the reason, you may believe that but you k